Typically, a solenoid valve comprises an armature movable between a first and second position. The extremes of these first and second positions are often defined by mechanical stops. Armatures can be moved in one direction by an electro-magnetic force generated by a coil of wire and moved in the opposite direction by a return spring. When the armature impacts a stop, it bounces.
In high speed fluid metering solenoids, armature bounce is a problem because each bounce of the armature, or valving element, meters a small uncontrolled amount of fuel into the engine, to the detriment of emissions. As can be appreciated, the leakage of fuel into the engine will result in very unfavorable fuel economy. At either end of its motion, the armature has kinetic energy as a result of its mass and velocity. With no means for dissipating that energy, it is returned to the armature by the elastic collision with the stop. Eventually, the energy is dissipated after a series of collisions and bounces. The bounce of the armature affects the operation of a fuel injector by prolonging or shortening the duration of injection, causing excessive wear in the valve seat area.
It is seen then that there exists a need for a means for damping the motion of an armature to diminish bounce, thereby diminishing the amount of fuel into the engine and the wear in the valve seat area.